Denial Management

Top 10 Claim Denial Reasons in Medical Billing

Fixing these ten common errors before submission stops most denials from happening.

Altair Health 5 September 2026

Initial claim denials reached 11.81% of claims in 2024, per Kodiak Solutions data covering more than 2,100 hospitals and 300,000 physicians. Kodiak also notes payers ultimately pay roughly 90% of claims, which makes most initial denials a delay in payment rather than a refusal of it.

The gap between the first answer and the final one is where the money sits, and closing it costs staff hours a small practice does not have. A denied claim is recoverable. A denied claim nobody works is not.

Ten reasons account for most of what comes back, and each one traces to a specific failure that happens before the claim leaves the practice. Naming that failure is the difference between an appeals queue and a claim that never gets denied.

1. Missing or inaccurate claim data, the reason billing staff name most often

Experian Health surveyed 250 people responsible for billing and claims decisions in June and July 2025. In the State of Claims 2025 report, 54% said claim errors are increasing and 68% said submitting a clean claim is harder than it was a year ago. The survey records what billing staff report rather than what claims data measures, so read it as the view from the desk rather than a rate.

The errors behind it are ordinary. A wrong date of service. A missing diagnosis code. A rendering provider who does not match the billing provider. A demographic field nobody completed. None of that needs a coding specialist to catch, which is what makes it expensive: the claim comes back, and a biller reworks it from the start. A scrubber that checks each claim against the payer's current policies before submission catches this class of error first. Our claims scrubbing guide covers what a complete pre-submission check includes.

2. Eligibility and registration errors, where the front desk decides a denial

In the same Experian survey, incomplete or inaccurate information collected at check-in ranked as the third most common cause of denials, with 26% of respondents tracing at least one in ten denials back to intake errors. A wrong policy number, a card that expired months ago, an eligibility check nobody repeated.

Coverage moves between the day a visit is booked and the day it happens. A plan switch, a new job, a premium that went unpaid. A single check at scheduling catches the problems that already existed and none of the ones that arrive afterwards. A second check the day before the appointment catches what the first one missed, and a third before the claim goes out catches the rest. Practices that stop at the first check are covering the smaller half of this risk.

3. Prior authorization, where denials move rather than disappear

Medicare Advantage insurers denied 4.1 million prior authorization requests in 2024, 7.7% of the nearly 53 million determinations they made, up from 6.4% in 2023, according to KFF. KFF notes these are service determinations rather than payment decisions on care already given.

The mechanism is shifting. Kodiak reports that authorization-related initial denials fell 7.7% in 2024 while medical necessity denials rose 5% and requests for more information rose 5.4%, each a relative change in the rate rather than a change in percentage points. The volume holds while the reason printed on the remittance changes, from an outright refusal to a request for documentation that delays payment just as well.

One trap causes most of the rest. An authorization covers a procedure, a date range and a rendering provider. Change any of the three and the claim fails against an authorization that still exists on paper. Our prior authorization guide covers how the requirements differ by payer.

4. Medical necessity, where the note decides the outcome

A medical necessity denial is rarely a disagreement about the medicine. It is a documentation gap. If the diagnosis codes submitted do not map to the service billed, the payer reads that as unsupported, whatever the care was.

This is the category where appeals help least, because an appeal can only argue from the note that already exists. Clinical detail that does not answer the payer's stated coverage criteria stays unpersuasive on the second reading. The work sits upstream, in what the provider records at the time: the specific clinical indicators that justify the service, next to the diagnosis code attached to it.

5. Coding errors, and what they actually cost a practice

The figure quoted most often here is a $631 average coding denial, and a practice should ignore it. It comes from MDaudit's 2024 benchmark report, and it is a blend across care settings that hospital inpatient claims dominate at roughly $10,000. The professional setting, which is what a physician practice bills, averaged $140, up 24% from the year before. Hospital outpatient sat at $825. Anyone quoting $631 to a practice is quoting somebody else's number.

MDaudit also attributes part of the 2024 increase to the Change Healthcare cyberattack, which held up payment through the middle and back end of the revenue cycle for months, so 2024 reads as an unusual year rather than a trend line.

The mistakes themselves are familiar: the wrong procedure code, a diagnosis and procedure that do not support each other, a code that retired, or upcoding aggressive enough to trip an audit flag. Prevention here is mechanical. Build code validation into claim creation, cross-walk diagnosis against procedure before submission, and keep coder education current with what each payer accepts, since that moves year to year.

6. Bundling, unbundling and modifier errors

Unbundling happens when a practice bills component procedures separately although a single bundled code covers the combination. Payers run automated edits that catch it the moment the claim arrives, and in an audit it can be read as a fraud indicator rather than a mistake.

Modifier errors are the close relative: a missing modifier, one the payer does not accept, or the wrong modifier for the place of service. They cluster in outpatient surgical claims and turn up often in post-payment audits. A practice running no equivalent logic on its own side is always reacting a step behind the payer. Closing that gap takes a scrubber carrying current NCCI edits and payer-specific modifier requirements, updated when a payer changes them rather than once a year when the code sets refresh.

7. Duplicate claim submissions, a workflow slip that reads as fraud

Duplicates start honestly. A biller resubmits because the original claim seems to have vanished, with no way to confirm that it is still sitting in adjudication. Without live claim status, a guess is all anyone has.

Payers auto-deny duplicates as routine, and a pattern of them can escalate into a fraud review, which turns a workflow problem into a compliance one. The scenarios repeat: a claim goes to the primary payer and then to the secondary before the first remittance returns, or a system fires the same claim twice and nobody notices. The fix is procedural. Track every claim by status from submission through adjudication, and require somebody to confirm that status before any resubmission.

8. Timely filing, and why there is no single deadline

Medicare allows one calendar year from the date of service. State Medicaid programs run shorter and vary widely, with Texas at 95 days and New York at 90. Most large commercial payers publish no national default at all, because the window lives in the participation agreement rather than in a manual. A single brand can run several windows at once: Blue Cross Blue Shield of Texas allows 180 days on HMO plans and 365 on PPO.

This is also the hardest denial to overturn. The coding, the documentation and the medical judgment stop mattering once the window closes.

The claims that miss it are the ones nobody was watching. A claim parked in a work queue through a staff change. A claim waiting on information nobody marked urgent. A secondary bill delayed long enough that the second payer's window closed first. An aging report sorted by each payer's actual deadline catches those. One built on a blanket 90-day assumption does not, and that assumption is wrong for most of the payers a practice bills. Our payer guides hold the current filing and appeal windows by payer.

9. Credentialing and enrollment mismatches, which stop a whole provider

This category does not block one claim. It blocks every claim attached to a provider, which puts it on a different scale from the other nine.

The mismatches take a few recognizable shapes. A claim billed under the group NPI for a service rendered under an individual NPI, with no linkage on file between the two. A provider credentialed with the plan, but a date of service that falls outside the effective date the payer holds. A provider enrolled at one location who saw the patient at another, which happens more as practices open second sites. Payer adjudication systems now catch all three automatically.

Preventing it takes a tracking system holding enrollment status, effective dates and NPI linkage payer by payer, one that flags a credential before it lapses rather than after the denials arrive.

10. Telehealth place of service and modifier errors

Three things have to line up for a telehealth claim to clear. The correct place-of-service code. The correct modifier, which is 95 at some payers and GT at others. And confirmation that the payer still covers the service at all.

Coverage diverged sharply once the public health emergency ended. One plan kept a service, the next dropped it, and several revised the terms without telling the practices billing them. No published benchmark tracks telehealth denials as their own category, so treat any growth figure quoted at you as unverified. The requirement stands regardless of what the trend line does: a payer-specific coverage and modifier matrix, kept current, and modifier validation before the claim goes out.

The ten reasons, and the one habit that prevents them

Read across all ten and the same three shapes appear. A data error caught too late. A payer policy that changed without the practice knowing. A workflow gap that let a known risk sit until it became a denial.

Appeals do not solve any of them, and running the operation around appeals gets the order backwards. Every one of the ten has a prevention point that sits before the claim leaves the building. Practices with low denial rates check data at the point of entry, verify eligibility more than once, track authorizations by expiration date, and update payer policies when the payer changes them rather than at an annual review. Our denial code reference covers what each CARC actually requires.

That last habit is the one that separates practices, and it is the hardest to keep. Payers revise on their own schedule and give little useful notice, so the advantage belongs to whoever updates first. Most practices keep that knowledge in one biller's head and lose it when that person leaves.

Altair runs eligibility verification, authorization tracking, claim scrubbing against each payer's current policies, denial work and appeals, and keeps what it learns about each payer in the system rather than in a person. Altair's own in-house billers own the exceptions the automation should not decide. The practice hires no one, manages no one, and keeps the EMR and clearinghouse it already uses. See how Altair runs denial management.

Treating denials as a cost of doing business has a price, and it is paid quietly, in revenue the practice already earned and then wrote off. Treating them as preventable compounds the other way, one billing cycle at a time.

The ten reasons, and where each one is prevented

Common questions